A　pilot-plant　sequencing　batch　reactor　(SBR)　with　a　working　volume　of　54　m　was　used　in　the　experiment　on　biological　nitrogen　removal　via　nitrite　from　municipal　wastewater　with　low　COD/N　ratio　for　saving　energy　and　carbon　sources.　At　normal　water　temperature,　the　feasibility　of　achieving　and　stabilizing　nitrogen　removal　via　nitrite　from　municipal　wastewater　with　the　low　COD/N　ratio　(average　2.16)　was　investigated.　The　obtained　resulted　showed　that　the　total　nitrogen　(TN)　in　the　effluent　was　less　than　3　mg/L　and　the　advanced　nitrogen　removal　was　obtained　through　application　of　step-feed　operation.　Moreover,　by　using　the　real-time　control　strategies,　the　nitrifying　communities　were　optimized.　Thus,　under　normal　dissolved　oxygen　(DO)　condition,　nitrogen　removal　via　nitrite　was　successfully　achieved　at　the　range　of　temperature　between　12°C　to　26°C,.　Nitrogen　removal　via　nitrite　kept　the　long-term　stability　(180　days)　and　the　average　NO2-N/NOx-N　ratio　was　above　95%.　The　fluorescence　in　situ　hybridization　(FISH)　was　performed　to　analyze　the　quantitative　changes　of　nitrifying　microbial　communities　in　the　activated　sludge.　The　results　also　indicated　that　ammonia-oxidizing　bacteria　(AOB)　became　the　dominant　nitrifying　bacteria　and　nitrite-oxidizing　bacteria　(NOB)　had　been　washed　out　of　the　activated　sludge.　It　indicated　that　the　nitrifying　microbial　communities　were　optimized.